1. Field of the Invention
The present invention relates to a dyeing method of dyeing a plastic, lens and a dyeing device.
2. Description of Related Art
Conventionally, a dip dyeing method has been adopted in most cases as one of dyeing methods of dyeing plastic lenses for spectacles. This dip dyeing method includes the steps of preparing a dyeing solution by mixing disperse dyes of primary colors of red, blue, and yellow at a predetermined ratio and dispersing the mixture in water; heating the dyeing solution to about 90° C.; and dipping a plastic lens into the heated solution, thereby dyeing the lens.
As an alternative to the dip dyeing method, there has been proposed a vapor deposition dyeing method, which is for example disclosed in U.S. Pat. No. 6,520,999 (Japanese patent unexamined publication No. 2001-59950). This method includes heating a sublimatable dye under vacuum to sublimate the dye and vapor deposit the sublimed dye onto a lens, thereby dyeing the lens. According to this vapor deposition dyeing method, a lens made of a material hard to dye by the conventional dip dyeing method can also be dyed and additionally working conditions can extremely be improved.
If the dyeing is repeatedly performed by the above vapor deposition dyeing method, however, there way be cases where lenses are dyed in different color densities from desired ones depending on the condition in each dyeing operation.
Furthermore, a hard-coating treatment is well known to enhance the surface strength (hardness) of a lens. Such hard-coated lens is desired to be dyed by the vapor deposition dyeing method.